1. Field of the Invention
The present invention relates to a thermionic electron source adopting carbon nanotubes.
2. Discussion of Related Art
Carbon nanotubes (CNT) are a carbonaceous material and have received much interest since the early 1990s. Carbon nanotubes have interesting and potentially useful electrical and mechanical properties. Due to these and other properties, CNTs have become a significant contributor to the research and development of electron emitting devices, sensors, and transistors, among other devices.
Generally, an electron-emitting device has an electron source using a thermal or cold electron source. The thermal electron source is used by heating an emitter for increasing the kinetic energy of the electrons in the emitter. When the kinetic energy of the electrons therein is large enough, the electrons will emit or escape from the emitters. These electrons emitted from the emitters are thermions. The emitters emitting the thermions are named thermionic emitters.
Conventionally, the thermionic electron source includes a thermionic emitter and two electrodes. The two electrodes are located on a substrate. The thermionic emitter is located between two electrodes and electrically connected thereto. The thermionic emitter is generally made of a metal wire such as tungsten etc, boride or alkaline earth metal carbonate. When a thermionic electron source uses boride as its thermionic emitter, the substrate will transfer heat from the thermionic emitter to the atmosphere in the process of heating since the thermionic emitter is connected to the substrate. Thus, the thermions emitting property of the thermionic electron source will be affected. Furthermore, since the thermionic emitter adopting the boride or alkaline earth metal carbonate has high resistivity, the thermionic electron source using the same has greater power consumption and is therefore not suitable for applications involving high current density and brightness. What is more, the traditional thermionic emitter materials usually have the typical dimension of about 10 micron to centimeter. They are difficult to be made into the tiny scale for the precise device, especially the device arrays for the special function such as display etc.
What is needed, therefore, is a thermionic electron source with excellent thermal electron emitting properties and wearability, and can be used in flat panel displays with high current density and brightness, logic circuits, and other fields of thermal electron source.